Is it a Basic Ceiling or a Compound Ceiling? Its a known issue with Basic Ceilings, but ive NEVER seen one used on a real project, so it doesnt matter.

It is a compound ceiling. It also happens when I place them on levels I have created. It seems the best option would be for the family itself to be in the correct orientation, plenum on top, but since the Titus diffuser families are direct from the manufacturer I'm thinking this is an issue with my model.

This is actually a "feature" and not a bug. You're supposed to place them in an Reflected Ceiling Plan. That way they go in "upside down", which in the RCP means above the ceiling. It's dumb, but that's how it's intended to work. I've long since gotten into the habit of beginning my air device placement on an RCP view, which you should have in your MEP model anyway for architectural and lighting coordination.

My post will not directly help your issue, but as a side comment, most people have completely turned away from hosted Families, especially those that can be very repetitive throughout the project (you could have hundreds, even thousands of diffusers and grilles in a single project). In theory is sounds great, but there are too many inherent flaws. For instance, if an architect decides to delete a ceiling and redraw, instead of editing, and you get an updated file, this will break all the grilles from the host since "technically" the host was deleted. Now you have to re-host the orphaned Families one by one.

It's easier to just set a height rather than host. So try creating your own, or start with the default non-hosted air terminal families that are included in the stock library and go from there.

-TZ

Thank's for the tip Necro. I was still having issues with the diffusers being upside down while being placed in in the RCP but I messed around and have determined that the issue was caused from locating the diffusers with "Place on Work Plane" and selecting the level that the ceiling is hosted on. I was able to get the diffusers oriented properly by instead using "Place on Face" and selecting the actual ceiling in the RCP view.

I think I will be switching to un-hosted diffusers in my next project.

Before jumping all in with un-hosted consider how many times you'll need to reposition them with ceiling/wall changes. Face based hosted elements will follow changes most of the time and if they don't it's no more work to rehost them as it is to change the elevation of an un-hosted family.

I would firmly disagree with this, depending on the situation. Yes, in later versions of Revit, you can re-host in batch, but only on certain Families. One example would be ceiling diffusers - yes, you can pick multiple Families and re-host in batch, but it's nowhere near as easy as picking a selection of ceiling diffusers and simply inputting the offset. And re-hosting in batch is still a rarity in most cases.

An example of where I would firmly disagree would be face hosted elements that are very individual in nature, such as a thermostat (Communication Device family). These are found on columns, walls, etc. Rehosting these can be a pain during revision phases of the project. And on projects where you have multiple floors with exact or similar floorplans, a copy/paste always is preceded by a fingers crossed. Sometimes it's easier to just copy/paste and massage a little.

I'm in no way against hosted Families, my angle is this: always consider the trade-off. In my experiences, the trade-off is greater to leave things unhosted.

-TZ

Exactly my point

1. If you go with unhosted elements there is efficiency when placing and repositioning objects but inefficiencies because you will have to re-position objects each time the associated ceiling/wall moves.

2. If you go with face-based hosted elements there are efficiency gains when objects move with their host but inefficiency if/when they lose hosting and are in the wrong position.

So boils down to how often you'll see changes and how the host model is modified.

Why not use named reference planes? At least for stuff that is along the ceiling? Combined with a global parameter or two and it should (in theory) be really easy to adjust.